A magnetic recorder is widely used as a recorder for recording and saving information. Such a magnetic recorder aims at raising a storage density of the information per unit area. For example, width of a magnetic record track is narrowed and improvement in track density is aimed at. Therefore, improvement in raising storage density is achieved by raising the machining accuracy of a traveling device of the magnetic recorder. However, if width of the magnetic record track is narrowed, it becomes difficult for a reproducing head to trace the magnetic record track completely when reproducing the recorded signal. Therefore, even if the improvement is achieved depending only on the machining accuracy of the traveling device of the magnetic recorder, it has limitations.
On the other hand, the latest high-density magnetic recorder incorporates the mechanism of a servo control by the servo track in addition to the same improvement as the traveling device of the conventional magnetic recorder. This enables the track on the magnetic recorder to be traced completely by controlling the position of the magnetic recording head or the reproducing head to the traveling magnetic recorder.
The magnetic recorder that uses such servo control records the servo pattern beforehand on the magnetic recorder. And the magnetic recording head and the reproducing head determine the position of the track on the basis of the servo pattern and trace the track. By the above, width of the track can be narrowed and increase in track density is achieved.
And in the magnetic recorder that uses such a servo control, it is important that correct servo pattern is formed on the magnetic recorder. In order to form a servo pattern on a magnetic recorder, a medium writing device of exclusive use, which is a servo writer, is used.
Standardized reproducing output must be secured for the record signal written on the magnetic recorder by such a servo writer, therefore, the servo signal writing head and the circuit, the reproducing head for inspection and the circuit have been adjusted so that the servo signal can be written on the magnetic tape of a specific kind (for example, the magnetic tape with same magnetic coercive force and magnetic layer thickness).
For this reason, when servo pattern is formed on different kinds of magnetic tapes, reattaching work and change of conditions are required for the servo signal writing head or its circuit and the reproducing head or its circuit. For this reason, the servo writer is needed to be stopped for a long time, involving a problem in respect of productivity and cost.